A computer hard drive is a storage device that rapidly records data as magnetic pulses on spinning metal platters, usually made of ceramic and aluminum. It is the heart of the computer, pumping vital data to the rest of the system. A motor spins the platters at speeds ranging from 4,500 to 15,000 rotations per minute. Data is stored and retrieved from the platter by a read/write head, which moves over grooves in the spinning platters much like a record player's needle.
The faster a hard drive spins, the faster you can access and transfer data. But this can generate a lot of heat, causing the platters to expand and contract too much. This in turn can damage tracks or sectors on the drive, resulting in lost data. That's why most computers have cooling systems, like the power supply fan that keeps air inside the casing flowing. The rotation of the platters also creates air flow. Many hard drive manufacturers are now making platters out of glass and ceramic. These materials can be made thinner than aluminum platters and are better able to resist the heat generated during operation of the hard drive.
Microprocessor chips all have a "maximum" speed rating stamped on their case. Heat build-up can also limit a chip's speed. A chip is a collection of transistors and wires. All transistors leak electricity when they operate, and this creates heat. The faster a chip runs, the more heat it generates.